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Chapter 2 Book O The Nature of Sound Name ________Teachers____________ Class _________________________________ Test Date ____3/6/2014__________________ Chapter 2 –The Nature of Sound Outline Section 1-What is Sound? p. 30 - 35 I. Sound and Vibrations Note-Sound is caused by __vibrations________. Vibrations are complete back and forth motion by an object. A. Sound Waves *Note-A __sound wave________ is a longitudinal wave caused by vibrations and carried through a medium. B. Sound and Media *Note-Facts about sound: 1. Sound waves cannot travel through a __vacuum_______. 2. Sound waves exist even if no one hears them. 3. Air particles vibrate along the path of a sound wave. II. How You Detect Sound *a. __eardrum_________ -Sound waves cause the eardrum to vibrate. d *b. __cochlea__________-Movement of liquid inside the cochlea causes hair cells to bend. *c. __hammer________, __anvil______, & _stirrup_________. Bones in the middle ear that increase the size of the vibrations. The stirrup vibrates the oval window. *d. Electrical signals are sent to the __brain_________ through nerves. A. Making Sound Versus Hearing Sound III. Hearing Loss and Deafness *Note- __Tinnitus________-One of the most common types of hearing loss. Tinnitus results from long term exposure to loud sounds. a. Protecting Your Hearing Chapter 2 –The Nature of Sound Outline Section 2-Properties of Sound p. 36 - 41 I. The Speed of Sound *Note-The medium through which sound travels will affect its __speed_________. A. How the Speed of Sound Can Change Sound travels slowest through __gases__(air)_______. Sound travels faster though ____liquid________. Sound travels the fastest through __solids________. II. Pitch and Frequency *Note- __Pitch________ is how high or low the sounds seems to the listener. Pitch is affected by the __frequency_________ of the sound waves. A. Frequency and Hearing *Note-Humans can hear sounds that have frequencies between 20 and 20,000 Hz. Sounds that are too high for humans to hear are called __ultrasonic sound___. B. The Doppler Effect *Note-The __Doppler_Effect__________ is caused by the motion of the listener or the source of the sound. III. Loudness and Amplitude A. Energy and Vibration B. Increasing Amplitude *Note-The amplitude of a sound wave determines its ___loudness__________. C. Measuring Loudness *Note-The most common unit used to measure the loudness of sound is the ___decibels_______ (dB). IV. Seeing Amplitude and Frequency A. From Sound to Electrical Signal Oscilloscope: changes a sound wave (longitudinal) to a transverse wave Chapter 2 –The Nature of Sound Outline Section 3 Interactions of Sound Waves I. Reflection of Sound Waves *Note-An __echo________ is a reflected sound wave. Sounds waves reflect best off of smooth, hard surfaces. A. Echolocation *Note-Some animals use ___echolocation______ to find food or other objects. B. Echolocation Technology C. Ultrasonography II. Interference Of Sound Waves *Note-___Interference_____ is the combination of two or more waves that result in a single wave. Interference can occur when two instruments play the same note. *Notes *A-Constructive InterferenceCompressions of one wave overlap compressions of another wave to create a louder sound. *B-Destructive InterferenceAs the compressions of one wave overlap the rarefactions of another wave, the sound will be softer because the amplitude is decreased. III. A. Interference and the Sound Barrier *Note-A person experiences a __sonic_boom_________ when the shock waves reach their ears. B. Interference and Standing Waves *Note- A __standing wave____________ is a pattern of vibrations that looks like a wave at rest. *Note-See figure 8 on page 46-Frequencies two or more times the fundamental frequency are called __overtones____________. Resonance A. Resonance in Musical Instruments *Note-___Resonance____________ is when the sound of one object causes another object to vibrate. Chapter 2 –The Nature of Sound Outline Section 4-Sound Quality I. What is Sound Quality? *Note-The blending of pitches through interference produces an instrument’s ___sound quality____________. II. Sound Quality Instruments A. String Instruments B. Wind Instruments *Note-In a Wind Instrument ___vibrations____ cause standing waves inside its air column. C. Percussion Instruments *Note-__Percussion________________ instruments vibrate when they are struck.